New to VBA having checkbox problems

So I'm new to programing(2weeks). I am making a data box to find total a price for a project. I works with text boxes, check boxes and a button to find total.

I input the number of lemons and oranges, when I press the button it calculates how much it will cost based on prices that are pulled from the sheet.

Now I put the check box because there is a set quantity of one. I would like to add the price of "sugar" to the total price when it is checked.

Can some one help me get the check box add to total price ??

for example the data box looks like this: Thanks enter image description here

enter image description here